Simplified method for the identification of low mass ratio contact binary systems that are potential red nova progenitors

Abstract

This study presents a simplified method to identify potential bright red nova progenitors based on the amplitude of the light curve and infrared (J–H) colour of a contact binary system. We employ published criteria for contact binary orbital instability to show that the amplitude of the light curve for a given contact system with a low mass (<1.4M⊙) primary must be less than a specified value for it to be potentially unstable. Using this, we search the photometric data of a large survey to identify about 50 potential bright red nova progenitors. We analyse each of the survey photometry to determine the mass ratio and from the estimated mass of the primary, other physical parameters of the systems. We show that each system has physical characteristics indicating potential orbital instability. Using the absolute parameters from our sample, we model the expected instability separation and period for low mass contact binary systems.